Java AndroidViewModel没有零参数构造函数。如何解决这个问题?
我几乎在整个互联网上搜索了我的问题,却找不到我需要的答案。 对我的问题不是唯一的,但没有答案,这对我有帮助。 所以我决定自己去问 关于这个问题:Java AndroidViewModel没有零参数构造函数。如何解决这个问题?,java,android,viewmodel,Java,Android,Viewmodel,我几乎在整个互联网上搜索了我的问题,却找不到我需要的答案。 对我的问题不是唯一的,但没有答案,这对我有帮助。 所以我决定自己去问 关于这个问题: public class AuthActivityViewModel extends AndroidViewModel { Repository repository; private LiveData<List<User>> users; private LiveData<User> us
public class AuthActivityViewModel extends AndroidViewModel {
Repository repository;
private LiveData<List<User>> users;
private LiveData<User> user;
public AuthActivityViewModel(@NonNull Application application) {
super(application);
repository = new Repository(application);
}
public LiveData<List<User>> getUsers() {
users = repository.getUsers();
return users;
}
public LiveData<User> getUser(int userId) {
user = repository.getUser(userId);
return user;
}
public void addNewUser(User user) {
repository.insertUser(user);
}
public void updateUser(User user) {
repository.updateUser(user);
}
public void deleteUser(User user) {
repository.deleteUser(user);
}
}
public class AuthActivity extends AppCompatActivity implements AuthInteractionListener {
private FragmentManager fragmentManager;
private final ConnectionBroadcastReceiver connectionBroadcastReceiver = new ConnectionBroadcastReceiver();
private int limitOfOnWindowFocusChangedOperationForAuthActivity = 0;
private boolean isActivityRecreated;
AuthActivityViewModel authActivityViewModel;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_auth);
isActivityRecreated = true;
IntentFilter connectionIntentFilter = new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION);
registerReceiver(connectionBroadcastReceiver, connectionIntentFilter);
authActivityViewModel = new ViewModelProvider(this).get(AuthActivityViewModel.class);
}
...
}
错误:
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.android.findthepikachuupgradeversion2/com.example.android.findthepikachuupgradeversion3.view.AuthActivity}: java.lang.RuntimeException: Cannot create an instance of class com.example.android.findthepikachuupgradeversion3.viewmodel.AuthActivityViewModel
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3307)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3446)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2043)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:224)
at android.app.ActivityThread.main(ActivityThread.java:7548)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:539)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:950)
Caused by: java.lang.RuntimeException: Cannot create an instance of class com.example.android.findthepikachuupgradeversion3.viewmodel.AuthActivityViewModel
at androidx.lifecycle.ViewModelProvider$NewInstanceFactory.create(ViewModelProvider.java:221)
at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:187)
at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:150)
at com.example.android.findthepikachuupgradeversion3.view.AuthActivity.onCreate(AuthActivity.java:44)
at android.app.Activity.performCreate(Activity.java:7893)
at android.app.Activity.performCreate(Activity.java:7880)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1307)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3282)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3446)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2043)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:224)
at android.app.ActivityThread.main(ActivityThread.java:7548)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:539)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:950)
Caused by: java.lang.InstantiationException: java.lang.Class<com.example.android.findthepikachuupgradeversion3.viewmodel.AuthActivityViewModel> has no zero argument constructor
at java.lang.Class.newInstance(Native Method)
at androidx.lifecycle.ViewModelProvider$NewInstanceFactory.create(ViewModelProvider.java:219)
at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:187)
at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:150)
at com.example.android.findthepikachuupgradeversion3.view.AuthActivity.onCreate(AuthActivity.java:44)
at android.app.Activity.performCreate(Activity.java:7893)
at android.app.Activity.performCreate(Activity.java:7880)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1307)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3282)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3446)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2043)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:224)
at android.app.ActivityThread.main(ActivityThread.java:7548)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:539)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:950)
如何解决此问题?将以下依赖项添加到gradle应用程序模块级别
implementation'androidx.lifecycle:生命周期扩展:$lifecycle\u版本
扩展包括许多库,包括LiveData
,因此,通过添加它,您可以摆脱:
implementation'androidx.lifecycle:lifecycle livedata:$lifecycle\u版本
但生命周期扩展似乎已被弃用。有
解决这个问题的另一个依赖项
这是对的,它一直都是
lifecycle extensions工件弃用:使用上述弃用
对于ViewModelProviders.of(),此版本标记了
生命周期扩展中的最后一个API和这个工件现在应该是
被认为是完全不赞成的。我们强烈建议
在您需要的特定生命周期工件上(例如
生命周期服务,如果您正在使用生命周期服务和
生命周期流程(如果您使用的是ProcessLifecycleOwner),而不是
生命周期扩展,因为未来不会有2.3.0版本的
生命周期扩展
正如文档所引用的,您可以使用特定的生命周期工件:正如我们在评论中所讨论的,特定的生命周期器aritifacts是:
implementation“android.arch.lifecycle:runtime:$lifecycle\u版本
并保留您的其他lifecycler依赖项工件。当出现此异常时,每次启动您的应用程序?是的。每次。您都可以添加此
实现“androidx.lifecycle:lifecycle extensions$lifecycle\u version
。逻辑上不会更改,但只是以防万一……它可以工作!谢谢。但这有什么帮助呢?LiveData
是扩展中包含的库之一,但它也包含其他库,我怀疑丢失其中任何一个库都可能导致此异常,让我检查一下是否可以找到有关此异常的文档。仅请将“实现”androidx.lifecycle:lifecycle LiveData$lifecycle_version“替换为”实现“androidx.lifecycle:lifecycle livedata:$lifecycle\u version”,我的意思是,你错过了符号“:”。这是我想要给其他用户的,不是给我的。@RubenKubalyan你能添加implementation“android.arch.lifecycle:runtime:$lifecycle\u version吗“
而不是`扩展名,请参见..”。。保持相同的依赖关系这也解决了我的问题!但它似乎是生命周期的扩展。还有其他依赖项可以解决这个问题吗?@cshadowstar感谢您提出这个。。我真的很感兴趣。。我刚刚更新了答案。。问:安卓工作室是否警告过你们反对,或者你们是从文档中得到的。。。我仍然可以使用它,并且在as 4.0.2中没有任何警告。谢谢你这么做!在AS 4.0.1下,我也没有收到任何警告,当我试图弄清楚为什么这个解决方案能够解决我的问题时,我从文档中得到了这一点。祝你一切顺利:)
implementation "androidx.lifecycle:lifecycle-livedata:$lifecycle_version"
annotationProcessor "androidx.lifecycle:lifecycle-compiler:$lifecycle_version"
def room_version = "2.2.5"
implementation "androidx.room:room-runtime:$room_version"
annotationProcessor "androidx.room:room-compiler:$room_version"